Wireless duplex system.



R. PPUND.

WIRELESS DUPLEX SYSTEM.

APPLICATION FILED JUNE 4, 1910.

1,076,312, I Patented 0013.21, 1913.

2 SHEETSSHEET 1.

2 II II o 8 a O 1 N ll 0 o o 1 o o Fig.2

NV TOR WITNESSES. a I

R. PFUND. WIRELESS DQPLBX SYSTEM. APPLICATION TILED JUNE4,1910.

1,076,312. Patented Oct. 21, 1913.

2 SHEETS-SHEET 2.

wi lmmao mm ncoz UNITED STATES PATENT orrica RICHARD PFUND, OF NEW YORK,Y.

WIRELESS DUPLEX SYSTEM.

Specification of Letters recess.

Patented Oct. 21,1913.

Application filed nine 4, are semi No. 565,042.

multaneously transmitting and receiving wir'eiess signals without mutualinterference or in other words a duplex system.

The essential features of this d'uplex systern are a receiver circuitassociated with an aerial and ground circuit or so called openoscillation circuit, a special variable or fixed oscillation circuitdesigned for use as an artificial aerial and ground circuit, anauxiliary coil equally divided between the actu'al aerial and groundoscillation circuit and the special variable 0'1" fixed-artificialoscillation circuit and a variable or fixed exciting oscillationcircuit, 6. an oscillation circuit in which the oscillations employed intransmitting are produced, all so arranged that no effect i produced inthe receiver circuit by the oscillations originating in the excitingcircuit and employed for transmitting but only by the oscillationscreated in the actual aeria l and ground oscillation circuit by incomingwaves.

My invention may be best understood by reference to the accompanyingdrawings forming part of this specification which illustrate certaincircuits for applying this system but inasmuch as a wide range is periuissihle in the application of my invention without departing from theprinciple there of it is understood that my invention is not limited tothe particular circuits shown here with.

In the accompanying drawings only the i higlrfrequency circuits areshown the other circuits ordinarily associated therewith beingomittedfor the sake of clearness.

In said drawings Figure 1 diagrammatically represents the high frequencycircuits with the aerial-ground circuit 13-6 shown in conventionalmanner. Fig. 2 represents the same diagram as shown in Fig. 1 but withan oscillation circuit 19 substituted for the aerial-ground circuit 136shown in Fig. 1. for better explanation. Fig. 3 is a detailiillustration of the balance coil, showing hdwv it may be adjusted.

.one side of a" special variable or rise ClllatlOIl circuit 7 containingcapa ity 8,-

In Fig. 1 these high frequency circuits of my duplex system consist ofthe usual closed variable or fixed exciting oscillation circuit '1 inwhich the oscillations employed in transmitting are produced by thedischarge of a condenser 2 through a spark-gap of gaps 3, and a variableor fixed inductance .coil 4. One terminal 5 of this variable or fixedinductance coil 4:, is connected to 5 ground or its equivalent at 6' andalso to in'ducta'nce 9 and resistance 10, one a two,

or all of which may be variable for pur- 7o poses of adjustment. Thisspecial variable or fixed oscillation circuit 7 I prefer tocall' theartificial oscillation circuit. Theother' side of this special variableor fixed artificial oscillation circuit 7 is conn to one side of a coil12 and to the or ier side. of this coil 12 is connected the aerial I3.The exact center 14 of the coil 12 is con nected to the remainingterminal, 15 of the variable or fixed inductance c oi 'l 4. It will sonow be obvious that with proper adjustment of the special variable orfixedart'i' ficial oscillation circuit 7 with reference to theaerial-ground or s'o-ca'lled open. oscillation or radiating circuit l3-6, a b'al'ance,85-

may be obtained in the coil 12 due to equal and opposite currentsflowing'at som'e instant during transmission in the coil, 12 either toor from the point 14 and that these equal and opposite currents willturn tend to induce equal and opposite currents in the receiving coil 16inductively coupled with the coil 12 and therefore have no effect uponthe indicating apparatus 17 included" in the circuit of the coil 16,provided that this receiving coil 16 is also so situated with referenceto the coil 12, that the, exact electrical center of coil 16 coiu'cideswith the exact electrical center of the coil 1%, so that thesubstantially equal and opposing fields produced by the substantiallyequal and opposite currents flowing in the coil 12 from the point 14will tend to produce substantially equal and opposite eiiects in thecoil 16s In order to obtain the exact ,balance I propose to make 1175the coil 16 movable along the axis of the coil 12, as indicatedwby thedotted arrows between the coil 12 and the coil 16 of Fig. l and as shownin Fig. 3 where coil 16 is shown having handles 25 at either end, by

which it can be axially shifted within coil 12. I also inc lose both thecoil 12 and the ed. at 11 75 coil 16 in a conducting case or cage asindicated by the dotted line 18 in Fig. 1 in order to screen and protectthe balanced coils or circuits 12 and 16 from extraneous inductiveinfluence from other portions of the transmitter. This conducting caseor cage may be grounded, as indicated at 23 in Fig. 1. In order to stillfurther explain the principle and operation of my duplex system. I havesubstituted for the actual aerial ground oscillation circuit 13-43 ofFig. 1, the oscillation circuit shown at 19, in Fig. 2 which circuitcontains the capacity 20, the inductance 21 and the resistance 22,together representing the electrical equivalent of the aerial-groundoscillation circuit 136 of Fig. 1. Wit-h exact balance between the twooscillation circuits 7 and 19 of Fig. 2, respectively representing thevariable or fixed artificial oscillation circuit 7, and theaerial-ground oscillation circuit 136 of Fig; 1, it will now be obviousthat although no effect will be produced in the coil 16 by oscillatingcurrents originating in the exciting circuit 1 and flowing in oppositedi rections through the coil 12 from the point 14', this will not be thecase if such oscillating currents originate in the circuit 19 of Fig. 2,the electrical equivalent of the aerial-ground oscillation circuit 136of Fig. 1, because in the latter case these currents originating in thecircuit 19 flow through the coil 12 in but one direction at any instantinstead of entering the coil. 12 at the center 14' and flowing inopposite directions from said center.

The full line arrows in Fig. 1 represent the direction at some instantand the path of thesending currents in the coil 12 and the inducedcurrents in the coil 16 originating in the exciting circuit 1 while thefull line arrows in Fig. 2 represent the direction at some instant andthe path of the receiving currents originating in the circuit 19, or theelectrical equivalent aerial-ground circuit 136 of Fig. 1.

Having described my invention, I claim:

1. A system for the simultaneous transmission and reception, withoutmutual interference, of signals or. speech by means of electromagneticwaves comprising an aerialground radiating circuit, an artificialnonradiating balancing circuit, an auxiliary coil in series with boththe aerial-ground radiating circuit and the artificial non-radiatingbalancing circuit, a transmitting exciting circuit with one sideconnected to ground and the other side connected to the center of theauxiliary coil, a movable coil forming part of a receiving circuit ininductive relation to the auxiliary coil and both the entire receiverand the auxiliary coil contained in a grounded metallic screening caseor cage.

2. A duplex system for the simultaneous transmission from and receptionat one and the same station, and without mutual interference, of signalsor speech by means of electromagnetic waves comprising an aerialgroundradiating circuit, an artificial nonradiating balancing circuit, anauxiliary coil in series with both the aerial-ground radiating circuitand the artificial non-radiating balancing circuit, a transmitterexciting circuit with one side connected to ground and the other sideconnected to the center of the auxiliary coil, a movable coil formingpart of a receiving circuit in inductive relation to the auxiliary coiland both the entire receiver and the auxiliary coil screened from therest of the aerial ground radiating circuit, the artificialnon-radiating balancing circuit and the transmitting exciting circuit.

RICHA RD PFUND.

